1. Field of the Invention (Technical Field)
The present invention relates to capacitive sensors, particularly those employed in automotive vehicular environments.
2. Background Art
Sensor technologies are becoming increasingly important in the development of safety and convenience features of vehicles. Because of differing vehicle geometries and extreme environmental conditions to which they are subjected, the sensors presently available are deficient in many regards.
Automobile air bag systems are a well known means of attempting to reduce the likelihood of serious injury to passengers in collisions. These systems are designed to very quickly inflate an air bag in front of a passenger during a collision, so as to hopefully prevent the passenger from colliding with hard objects in the passenger compartment interior, particularly the steering column and/or the dashboard. Such systems typically sense that the vehicle is involved in a collision, by using an accelerometer to sense sudden deceleration of the vehicle. Rapid inflation of the air bag may be obtained by electrical ignition of a pyrotechnic substance which rapidly generates a volume of gas sufficient to inflate the air bag, or by electrical opening of a valve for release of compressed gas stored in a chamber which is part of the air bag system.
The performance of an air bag system, in terms of its success or failure in preventing serious passenger injury, may be critically dependent on facts concerning the initial position and subsequent motion of the passenger, which are not made known to the system by an accelerometer which senses deceleration of the vehicle as a whole. Passenger head motion is particularly important, due to the seriousness of head injuries. For example, if the passenger is seated too far forward, or has his/her head too far forward, occupying the space into which the air bag will deploy, the passenger may be seriously injured by the deployment of the air bag intended to prevent passenger injury. So there is dearly a need for passenger position sensing apparatus, which can prevent air bag deployment when the passenger is already too far forward when the collision begins.
But even if the passenger is not too far forward at the beginning of the collision, the passenger will tend to move rapidly forward, with the passenger""s head leading that motion, relative to the vehicle, as the vehicle rapidly decelerates, and will tend to move into the air bag deployment space, at least in the case of forward collisions, and may be too far into the air bag deployment space, before the completion of air bag deployment, to escape injury from the air bag deployment. There are a number of factors which may strongly influence the forward motion of the passenger, in addition to initial position, in ways which may vary markedly from one passenger to another. The relative forward motion of the passenger will depend strongly on whether the passenger has secured a seat lap belt and/or shoulder harness prior to the collision. The passenger""s motion may also be influenced somewhat by the strength of any tensing up reaction the passenger has to the collision, i.e., instinctively pushing forward with the feet against the floorboard to restrain forward motion of the body. Such a protective reaction may vary greatly from one passenger to another, and may be greatly reduced or wholly absent if the collision is too sudden, so that the passenger has no time to react, or if the passenger is intoxicated or otherwise impaired. Also variation of the crash intensity by itself will cause considerable variation in passenger acceleration. So there is a need for systems which account for various positional and motion data, and analyze that information in making the yes or no decision on air bag deployment. Overhead sensors offer an advantage over those previously known systems having beam-emitting sensors located in front of the passenger, as in air bag systems with acoustic sensors mounted on the steering column, for which the beam from the sensor will at times by blocked from operating by the hands and/or forearms of the driver.
The use of capacitive sensors offers advantages over beamxe2x80x94emitting sensors, since each capacitive coupling sensor functions by sensing the change in the capacitance of a capacitor, caused by the nearby presence of a person, an effect which is essentially instantaneous (since propagated at light speed), rather than requiring a finite, non-negligible beam travel time as in the case of an ultrasonic position sensor, and since the capacitive coupling sensor does not require transmission and detection of a beam which might be blocked. And the use of an overhead array of capacitive coupling proximity sensors, the signals from which are analyzed by a microprocessor, allows essentially instantaneous and continuous monitoring of passenger position and motion through triangulation based on the distances of the passenger to the various sensors of the array, so that the overhead sensor array can be used to accurately and continuously determine forexe2x80x94aft, diagonal, and lateral passenger motion. Since the passenger""s head will be closest to the overhead sensors, this method will be particularly sensitive to passenger head motion.
The current state of the art is reflected by the following patents: U.S. Pat. No. 5,702,123, to Takahashi et al., entitled xe2x80x9cAir Bag Apparatus for Passenger Seatxe2x80x9d; U.S. Pat. No. 5,653,462, to Breed et al., entitled xe2x80x9cVehicle Occupant Position and Velocity Sensorxe2x80x9d; U.S. Pat. No. 5,602,734, to Kithil, entitled xe2x80x9cAutomobile Air Bag Systemsxe2x80x9d; U.S. Pat. No. 5,549,323, to Davis, entitled xe2x80x9cPlastic Air Bag Cover Having an integrated Occupant-Sensing Sensor Modulexe2x80x9d; U.S. Pat. No. 5,512,836, to Chen et al., entitled xe2x80x9cSolid-State Proximity Sensorxe2x80x9d; U.S. Pat. No. 5,365,241, to Kithil, entitled xe2x80x9cAutomobile Air Bag Systemxe2x80x9d; U.S. Pat. No. 5,802,479, to Kithil, entitled xe2x80x9cMotor Vehicle Occupant Sensing Systems;xe2x80x9d U.S. Pat. No. 6,014,602, to Kithil, entitled xe2x80x9cMotor Vehicle Occupant Sensing Systems;xe2x80x9d U.S. Pat. No. 5,363,051, to Jenstrom et al., entitled xe2x80x9cSteering Capaciflector Sensorxe2x80x9d; and U.S. Pat. No. 5,118,134, to Mattes et al., entitled xe2x80x9cMethod and Apparatus for Protecting Motor Vehicle Occupantsxe2x80x9d.
Capacitive sensor arrays are employed in the art for detection of persons, including for presence and position within automobiles. Further representative of the art are U.S. Pat. No. 3,864,668, entitled xe2x80x9cSeat Belt Warning and Ignition Interlock Systemxe2x80x9d, to Bickford; U.S. Pat. No. 3,898,472, entitled xe2x80x9cOccupancy Detector Apparatus for Automotive Safety Systemxe2x80x9d, to Long; U.S. Pat. No. 4,796,013, entitled xe2x80x9cCapacitive Occupancy Detector Apparatusxe2x80x9d, to Yasuda et al.; and U.S. Pat. No. 4,887,024, entitled xe2x80x9cPerson Detecting Devicexe2x80x9d, to Sugiyama et al. U.S. Pat. Nos. 4,972,154 and 5,394,097, entitled xe2x80x9cApparatus and Method for Measuring Wood Grain Anglexe2x80x9d, and xe2x80x9cDielectric Sensorxe2x80x9d, respectively, to Bechtel, et al., exemplify one and two-sided fabrication of electrodes on traditional printed circuit (PC) boards.
The present invention provides apparatuses and methods addressing deficiencies in the prior art, as described in the description of the preferred embodiments, below. The present invention concerns systems for sensing characteristics of motor vehicles and occupants for purposes such as deployment of air bags during vehicle crashes, to monitor drowsy drivers, and to determine crash characteristics. More particularly it concerns systems in which the system operation is affected not only by information about the motion of the vehicle caused by crash forces, but also measured data concerning the motion of the passenger, so that the system will operate in a manner to minimize the risk of serious injury to the passenger. The present invention also incorporates a microprocessor having memory to track data and compare it to reference data, as well as an algorithm to compensate for temperature effects upon the sensors.
The present invention is of a force-detecting capacitive sensor comprising at least two electrodes integral with a transparency product. At least one of the electrodes can be a conductive membrane or coating that is also integral with the transparency product. The electrodes can be in a parallel or a non-parallel configuration. The transparency product can be glass, for example a vehicle windshield.
The present invention is also a system for detecting force which imparts momentary bending to a transparency product. The system is comprised of at least one force-detecting capacitive sensor integral with the transparency product. Preferably, the sensor or sensors are configured for discriminating different vehicle crash characteristics, and preferably work in conjunction with a vehicle occupant protection system having at least one occupant restraint device.
The present invention is also a system for detecting a visibility condition of a transparency product, and the system comprises at least one capacitive sensor integral with the transparency product that is able to distinguish between a visibility condition and an object in proximity to the transparency product. Preferably, the system operates in conjunction with a vehicle occupant protection system to distinguish between a vehicle occupant in proximity to the transparency product and condensed moisture on the transparency product. Preferably, the system further initiates a response to modify the visibility condition.
The present invention is further a method of compensating for long-term affects of temperature on a sensing system. The method includes the steps of determining the constant desired sensor output; determining low frequency shifts due to temperature affects; comparing the constant desired sensor output to the low frequency shifts due to temperature affects; and employing a compensation algorithm to account for the difference.
Additionally, the present invention is a vehicle occupant detecting capacitive sensor in combination with a conductive panel functioning as a vehicle airbag door and ground plane for the capacitive sensor. Additional capacitive sensors can be included, and all of the capacitive sensors are fabricated on a substrate material adjacent to the conductive panel. Preferably, the capacitive sensors are each assigned to at least one triangle for discriminating occupant proximity and providing data to an airbag controller. Each of the capacitive sensors are preferably circular.
The present invention is still further a method of configuring a capacitive sensor and a reference sensor on a dielectric substrate, and comprises the steps of fabricating a reference sensor and a capacitive sensor on a substrate; placing a monolithic ground on a reverse side of the substrate; attaching a printed circuit board to a deleted portion of the monolithic ground; connecting the reference sensor to electronic parts on the printed circuit board; and compensating for changes in capacitive sensor output which are not related to proximity of a vehicle occupant by comparing the capacitive sensor output to the reference sensor output.
The present invention also is a method of detecting head motion indications of a drowsy vehicle operator. This method comprises the steps of representing the drowsy vehicle operator""s head motion with a four-dimensional feature vector, training a feature detection network; utilizing a sleep detector to detect head motion that does not look like an alert operators head motion and does look like a feature associated with a sleep nod; customizing the sleep detector for individual vehicle operators; and identifying the operator of a vehicle and modifying sleep detector parameters based on historical data attributable to the identified operator.
The present invention is further still a capacitive occupant sensing system for a sunroof-equipped vehicle to monitor an occupant""s head position. The system consists of a nested circle capacitive sensor and at least one L-shaped capacitive sensor surrounding the nested circle capacitive sensor, and both the nested circle capacitive sensor and the L-shaped capacitive sensor are located adjacent the sunroof. Optionally, the system further comprises a dummy sensor located on the opposite side of the sunroof from the nested circle capacitive sensor and the L-shaped capacitive sensor. A method of sensing the occupant""s head position in the sunroof-equipped vehicle with a dummy sensor and a nested circle capacitive sensor array comprises the steps of positioning a dummy sensor on an opposite side of the sunroof from the nested circle capacitive sensor array adjacent the sunroof; deriving a composite head position from the dummy sensor head position and the triangulated head position from the nested circle capacitive sensor array; identifying the operator by comparing the head coordinates of the operator to historical data attributable to the identified operator; and updating parameters which identify non-impairment conditions of the operator.
A primary object of the present invention is to provide capacitive sensing arrays and systems for detecting force upon a transparency object, for sensing occupant head position, for determining vehicle crash characteristics, and for operating in conjunction with a vehicle occupant safety system.
Another object of the present invention is to provide a means for a reference sensor to be near a capacitive sensor.
Still another object of the present invention is to provide an electrode for capacitive sensing made from a conductive coating.
Yet another object of the present invention is to combine a capacitive sensor with a conductive panel that functions as a vehicle airbag door, as well as a ground plane for the capacitive sensor.
Yet still another object of the present invention is to provide a detection algorithm for detecting head motion indications of a drowsy vehicle operator specific to individual operators.
A primary advantage of the present invention is that a can distinguish between moisture upon a transparency product and an object near a transparency product.
Another advantage of the present invention is that is compensates for long-term temperature effects upon sensors.
Another advantage of the present invention is that it identifies a vehicle operator and adjusts vehicle safety systems to be specific to the identified operator.
Yet another advantage of the present invention is that it defines a capacitive sensor array, including a dummy sensor, that is effective in detecting an occupant""s head position for a sunroof-equipped vehicle.
Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.